The proverbial phrase “you are what you eat” is often an encouragement to eat healthy. In this article, we will explore how true that statement is when it comes to Western and Mediterranean diets. Western diets typically include foods high in calories, sugar, saturated fat, and food additives. Mediterranean diets, on the other hand, revolve around plant-based foods (i.e., vegetables, fruits, and cereals), fish, and olive oil. Researchers have determined that Western diets can lead to increased cognitive decline and risks of acquiring Alzheimer’s disease while Mediterranean diets have neuroprotective properties.
What Are The Disadvantages Of A Western Diet?
Western diets stimulate neuroinflammation, insulin resistance, and reduced neurotrophic content, which are all key factors for Alzheimer’s disease progression.
Neuroinflammation & Diet
Neuroinflammation is associated with cognitive dysfunction and Alzheimer’s disease pathogenesis. This is evidenced in the increased number of activated microglial cells and proinflammatory cytokines in postmortem brain tissue of Alzheimer’s patients. Proinflammatory cytokines result in disrupted hippocampal synaptic plasticity, neuronal death, cortical thinning, and reduced brain volume. Researchers believe that a Western diet leads to neuroinflammation. A study by Graham et al., found that the stereotypical Western diet exacerbated plaque load in the hippocampus of mice. Such data is evidence that a Western diet is capable of acting as a driver for Alzheimer’s disease.
Western diets also bring about insulin resistance. Typically, insulin signaling will prevent formation of Aβ plaques and tau hyper-phosphorylation; however, a Western diet can lead to the formation of Aβ plaques. Numerous clinical and epidemiological studies, along with animal models of Alzheimer’s and postmortem Alzheimer’s brains, support that there is a direct link between insulin resistance and Alzheimer’s. In a study led by Janson, researchers found that more than 80% of Alzheimer’s patients show signs of abnormal blood glucose levels. There is a link between decreases in insulin sensitivity and impaired cognitive performance.
A recent study done on swine fed a high-fat, high-fructose, and high-cholesterol diet for 10 weeks also showed reduced insulin-stimulated Akt signaling in the prefrontal cortex. Such evidence further demonstrates a Western diet’s influence on the onset of Alzheimer’s.
Brain-Derived Neurotrophic Factor
A Western diet also has a negative impact on brain-derived neurotrophic factor (BDNF). Researchers found that with Alzheimer’s, there is a reduction in synaptic plasticity and BDNF content in the hippocampus and parietal cortex regions. With a reduction in the circulation of BDNF, there is an acceleration of cognitive decline in patients with Alzheimer’s.
Using animal models to study the effects a Western diet has on BDNF, researchers conducted a study that involved feeding participants a diet high in saturated fatty acids (SFAs); results show that BDNF significantly decreases over the course of the study, and these reductions correlate with reduced cognition. Molteni et. al. also observed this in a separate study when feeding rats a high sucrose diet for 90 days. The results of this study demonstrated decreases in hippocampal BDNF content and cognition, as shown by a reduction of performance in a water maze.
What Are The Advantages Of A Mediterranean Diet?
The Mediterranean diet has become known for its neuroprotective properties that appear to delay or prevent the onset of Alzheimer’s. Unlike the Western diet, research shows the Mediterranean diet significantly improves insulin sensitivity, possesses anti-inflammatory effects, and increases production of BDNF. Why is this the case? It may stem from the fact that the Mediterranean diet consists of polyunsaturated fatty acids, polyphenols, and antioxidants. Researchers believe all of these factors directly reduce Alzheimer’s risk and improve cognition.
High In Polyunsaturated Fatty Acids
The Mediterranean diet is high in polyunsaturated fatty acids (PUFA). According to scientists, PUFAs are responsible for improved cognition and slowing the onset of Alzheimer’s. In a Mediterranean diet, researchers believe the high levels of PUFAs are due to fish intake. Fish is rich in long-chain omega 3 fatty acids including α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Omega-3 fats also significantly improve cognition, as Alzheimer’s Assessment Scale scores demonstrate.
High In Polyphenols
Foods rich in polyphenols (e.g., fruits, vegetables, olive oil) comprise the Mediterranean diet. Polyphenols are directly associated with improved cognition and reduced inflammation and Aβ pathologies. In a study done on postmenopausal women (a population at higher risk of acquiring Alzheimer’s), increased uptake of polyphenols resulted in reduced rates of cognitive decline. Additionally, polyphenol-rich foods, such as blueberries, have been shown in recent studies to inhibit inflammatory proteins and increase BDNF levels in brain regions associated with learning and memory.
Rich In Dietary Antioxidants
Fruits and vegetables, which are full of antioxidants, are an abundant part of the Mediterranean diet. There are associations between high antioxidant intake and reduced Alzheimer’s progression. In fact, recent attention has linked vitamin E, which acts as an antioxidant, to lower levels in plasma and cerebrospinal fluid found in patients with Alzheimer’s. As a result, researchers believe that high levels of vitamin E present in Mediterranean diets may be key for Alzheimer’s prevention. This has led to further studies on the benefits of vitamin E supplementation.
Based on current research, one thing is clear: Diets are directly linked to causes and treatments for chronic conditions such as Alzheimer’s and obesity. Adapting a diet that will improve long-term health impacts is essential.